1. Field of the Invention
The present invention relates to surgical lead bodies which provide electrical stimulation to nerve tissue of a patient. More particularly, but without restriction to the particular use which is shown and described, the present invention relates to a surgical lead body having a minimum cross section such that the surgical lead body may be percutaneously implanted through a modified Tuohy needle having an oblong shaped opening.
2. Description of the Related Art
It is known that nerve tissue stimulation is used to treat numerous neurological disorders, including, but not limited to, cerebral palsy, multiple sclerosis, amyotrophic lateral sclerosis, dystonia, and torticollis. It is further known that nerve tissue stimulation is useful to treat intractable malignant and nonmalignant pain. Stimulation of nerve tissue of the spinal cord, for example, is often accomplished through implanted medical leads in the epidural space of the spinal cavity. The implanted lead defines a lead body which includes neural stimulation electrodes that conduct electrical stimulation signals from a stimulation source, such as implantable pulse generators, to targeted nerve fibers in the epidural space. These medical leads may be percutaneous lead bodies which have a cylindrical shape with cylindrical electrodes spaced along the body of the lead. Also, the medical leads may be surgical lead bodies with electrodes spaced in an array on a paddle-type lead body.
As conventional, the percutaneous lead body is introduced into the epidural space of the spinal cord using a needle and stylet. The needle (commonly referred to as a Tuohy needle) and stylet are interested into the targeted spinal column area between adjacent vertebrae until the tip of the needle and stylet are positioned into the epidural space. The stylet is withdrawn and a percutaneous lead body is inserted through the opening or lumen of the needle into the epidural space and positioned at the targeted stimulation area. The needle is then withdrawn leaving the percutaneous lead body in the desired stimulation position. Drawbacks encountered with known percutaneous lead bodies include migration or movement of the lead body after it is implanted. In addition, the cyclindrical shape of the electrode in the percutaneous lead body generates omni-directional stimulation instead of one-directional, focused stimulation.
The surgical lead body which is typically a paddle-type lead body often has a rectangular, flat cross-section. Spaced in an array on one side of the paddle are the electrodes. The array of electrodes provides better stimulation coverage of the targeted nerve tissue than a percutaneous lead body. In contrast to the percutaneous lead body, however, the surgical lead body is surgically implanted into the epidural space. This requires a physician to perform a laminotomy, laminectomy, or similar procedure, prior to the insertion of the surgical lead into the epidural space. Once implanted, the surgical lead having the flat, rectangular shape is generally more stable than a percutaneous lead and provides one-directional stimulationxe2x80x94stimulation more focused than a percutaneous lead body. A drawback with the surgical lead body, however, is the performance of a laminotomy or similar surgical procedure. Anesthesiologists who frequently provide the nerve tissue stimulation for a patient are often prevented from using the surgical lead body as the laminotomy procedure is generally outside the scope of their practice.
Accordingly, it is an object of the present invention to provide an implantable lead body that provides the advantages of the surgical lead body but does not require performing a laminotomy, or other surgical procedure, prior to implantation. It is another object of the present invention to provide a lead body that may be percutaneously implanted at the targeted nerve tissue. It is yet another object to provide a lead body having the stability of a surgical lead. Another object is to provide a lead body having an array of spaced electrodes for better stimulation coverage of the targeted nerve tissue. Still another object of the present invention is to provide a lead body having one-directional, focused stimulation.
Briefly, in summary, the present invention comprises bonding together two percutaneous lead bodies, resulting in the functional equivalent of a surgical lead body. The inventive medical lead body forms columns of electrodes which are either adjacent to or offset from each other, thus forming an array of electrodes. The bonding of the percutaneous lead bodies is accomplished by a plurality of urethane bridges molded to each of the percutaneous lead bodies. The plurality of bridges provides structural integrity to the medical lead yet permits the desired flexibility of the lead body. One side of the inventive medical lead body is xe2x80x9cmaskedxe2x80x9d or coated with a suitable non-conductive material. The masking of one side of the medical lead body makes that side of the lead body non-conductive and effectively directs the stimulation signals transmitting from the cylindrical electrodes toward the desired stimulated area for focused stimulation. In contrast to the surgical lead body, the medical lead body of the present invention may be percutaneously implanted. The percutaneous implantation is achieved by inserting the inventive medical lead body through a modified Tuohy needle having an oblong cross-section or other similar needle, such as, the needle disclosed in U.S. patent application Ser. No. 09/303,045, now U.S. Pat. No. 6,249,707 which is incorporated herein by reference.
Examples of the more important features of this invention have been broadly outlined above in order that the detailed description which follows may be better understood and so that contributions which this invention provide to the art may be better appreciated. There are, of course, additional features of the invention which will be described herein and which will be included within the subject matter of the claims appended hereto.